The present invention relates to an electronic timepiece having a power generating function of detecting the power generating state of power generating means, thereby causing a display section to display a detection state, and more particularly to an electronic timepiece having a power generating function of detecting whether a state in which the power generating means generates power or a state in which the power generating means does not generate power, thereby causing display means to display the state.
There has been known an electronic timepiece including power generating means for converting an external energy such as a light energy or a mechanical energy into power to be utilized for time display.
Examples of the power generating means include power generation by a solar cell or the kinetic energy of a oscillating weight, power generation by a difference in a temperature on both terminals of a thermocouple and the like.
The electronic timepiece having such power generating means generally has storage means for storing power generated by the power generating means, for example, a secondary battery or a capacitor.
There has been practically used an electronic timepiece for displaying the storage level of the storage means (the residual storage level) by a modulated hand motion with changing a hand moving mode and the like, for example. Japanese Patent Application Laid-Open (JP-A) No. 60-185188 has disclosed an electronic timepiece for displaying the storage level by such a modulated hand motion.
Furthermore, Japanese Patent Publication (JP-B) No. 7-89154 and the like have disclosed an electronic timepiece for stopping a hand motion when the storage level is very low and for restarting the hand motion to perform time display when the storage level is recovered to a predetermined level or more by subsequent charging.
With reference to FIG. 15, description will be given to an electronic timepiece having a power generating function of the prior art.
FIG. 15 is a block diagram illustrating the structure of a circuit of an electronic timepiece having a power generating function of the prior art.
Storage means 720 such as a lithium ion secondary battery and control means 750 having a timing function are connected in parallel with power generating means 710 which is a solar cell. Moreover, control means 730 having a diode 732 is provided among the storage means 720, the control means 750 and the power generating means 710. The control means 730 serves to control the charging or storage of the storage means 720.
The control means 750 for timing serves to move an hour hand, a minute hand and a second hand by using a stepping motor and a decelerating train wheel and is generally used for an electronic timepiece.
To the negative electrode side of the storage means 720 is connected storage level detecting means 742 for measuring a difference in an electric potential between the terminals of the storage means 720 and comparing the difference in an electric potential between the terminals with a predetermined difference in an electric potential. The detecting means 742 is an amplifier circuit for outputting a high level (1) when an input voltage is higher than 1.3 V and otherwise outputting a low level (0).
In FIG. 15, a signal output from the detecting means 742 is indicated as the reference numeral S20. The detecting means 720 decides that the storage level is sufficient when the signal S20 is indicative of the high level. At this time, an ordinary one-second hand motion is carried out (by one-step to be performed every second). The detecting means 720 decides that the storage level is low when the signal S20 is indicative of the low level. The hand motion to be performed at this time is a two-second hand motion (a two-step hand motion to be performed at a short interval of 2 seconds, such a hand motion which is different from an ordinary hand motion is referred to as a modulated hand motion).
In the electronic timepiece described above, when the power generating means 710 starts power generation, a current mainly flows from the power generating means 710 to the storage means 720 through the diode 732 and the storage means 720 is charged.
When the storage level of the storage means 720 reaches approximately 1.0 V which is enough to operate a step motor of the control means 750 which is not shown, the control means 750 is started so that the hand motion is started to be operated. In this case, the storage voltage of the storage means 720 has not reached 1.3 V yet. Therefore, the signal S20 is indicative of the low level and the two-second hand motion is carried out.
When the power generation of the power generating means 710 is consecutively carried out and the storage means 720 is continuously charged, an absolute value of the difference in the electric potential between the terminals of the storage means 720 exceeds 1.3 V. When the absolute value of the difference in the electric potential exceeds 1.3 V, the signal S20 is indicative of the high level and the hand motion is switched into the one-second hand motion in the ordinary state by the control means 750.
Since, such an electronic timepiece detects the storage level of the storage means 720 to control the hand motion and informs a user whether the hand motion can be surely performed based on the detected storage level, it is convenient.
In the above-mentioned electronic timepiece according to the prior art, however the warning of the residual storage level of the storage means 720 by the modulated hand motion makes no difference during power generation and non-power generation. Therefore, even if it can be known that the storage means 720 is fully stored, it cannot be known whether or not the power generating means 710 generates power well. Moreover, even if the power generation is performed by the power generating means 710, the modulated hand motion is continued until the storage level of the storage means 720 becomes predetermined level or more. Therefore, the hand motion different from the ordinary hand motion is carried out for a comparatively long period of time, so that it makes the users anxious.
For amusing, in the case where the user wants to show that his or her electronic timepiece which looks like an ordinary timepiece has a power generating function or the user wants to ascertain that the power generating means 710 is normally operated, it is impossible to meet such a user""s demand.
In addition, when the electronic timepiece according to the prior art is left for a comparatively long period of time, the storage level of the storage means reaches approximately 0 so that the electronic timepiece does not perform as a timepiece. For this reason, it is necessary to cause the power generating means to function in use, thereby storing power in the storage means and then performing timing. In recent years, however, there has been required an electronic timepiece which does not have a time display function even if it is left for a longer period of time.
In order to solve the above-mentioned problem, it is an object of the present invention to provide an electronic timepiece having a power generating function which can immediately be seen as to whether or not the power generating means is set in a power generating state or a non-power generating state. Moreover, it is another object of the present invention to provide an electronic timepiece having a power generating function which can indicate the charging state of storage means. It is a further object of the present invention to provide an electronic timepiece having a power generating function which can control the level of consumed power based on the levels of power generation and storage, thereby keeping a time display function even if the electronic timepiece is left for a long period of time.
In order to achieve the above-mentioned object, the present invention provides an electronic timepiece having a power generating function comprising power generating means, control means for working on receipt of power supply from the power generating means, and display means for displaying a time by the work of the control means, comprising detecting means for detecting a state of the power generating means and deciding means for deciding whether or not the power generating means generates power based on a detection signal sent from the detecting means, wherein the power generating state is displayed on the display means based on the decision of the deciding means.
Whether or not the power generating means generates power can be decided based on the difference in an electric potential between both terminals of the power generating means. For example, whether a power generating state capable of gaining sufficient power can be known as whether or not an absolute value of the difference in an electric potential is greater than a predetermined value. It is also possible to provide storage detecting means for detecting the storage level of the storage means.
The display of the power generating state can be carried out by the modulated hand motion of a hand in an analog type timepiece, and by digitally displaying a mark or the like in a digital type timepiece.
Consequently, the electronic timepiece according to the present invention can inform a user whether or not the power generating means generates power by the change of the hand motion state or the display of the display section.
Moreover, the time display operation of the control means may be changed depending on the generated power level by the power generating means. It is preferable that the absolute value of the difference in an electric potential between the terminals of the power generating means should be compared with a predetermined value, thereby changing the time display operation. The time display operation may be changed depending on the storage level of the storage means.
Consequently, it is also possible to display the level of power generation of the power generating means and the storage level (the residual storage level) of the storage means.
Moreover, the storage level of the storage means can particularly be detected. For example, consequently, also in the case where the storage level of the storage means is very low, an ordinary hand motion can also be carried out if the power generating means continuously supplies a predetermined power level.
Furthermore, it is also possible to provide switch means for selectively switching the supply of power from the power generating means into the detecting means. The switching means can perform switching automatically or manually.
Consequently, when the power generating state of the power generating means is detected, the supply of the power from the power generating means to the storage means or the control means can be blocked.
Moreover, when the absolute value of the generated power level by the power generating means and/or the power level stored in the storage means is smaller than a predetermined value, a part of the time display operation or the whole time display operation to be performed by the control means can be stopped in order to reduce the power consumption. It is preferable that a second hand or all the hands should be stopped to reduce the power consumption. In this case, it is preferable that the second hand should be first stopped and all the hands should be stopped after the passage of a predetermined time.
With such a structure, in the case where the generated power level by the power generating means and/or the storage level of the storage means are reduced, the power consumption can be suppressed. Moreover, even if the power generating means does not generate power, a time display function can be kept for a long period of time. When the electronic timepiece is to be used after it is left for a long period of time, it is possible to quickly move the hand, thereby displaying an accurate present time.